The Asymmetric Chelate-Claisen Rearrangement as a Key Step in the Syntheses of Non-Proteinogenic Amino Acids

Abstract

Allylic esters of TFA-protected amino acids undergo asymmetric Claisen rearrangements in the presence of cinchona al- kaloids, giving rise to -unsaturated amino acids in a highly stere- oselective fashion. The products are useful precursors for the short and efficient synthesis of more complex compounds such as substi- tuted 4-hydroxyornithines and iminosugars. Starting from the un- saturated amino acids, iodolactonization, bicylization and opening of the lactone ring with nucleophiles such as amino acids or pep- tides provide hydroxyproline derivatives directly incorporated into peptides.